AERO RADIO
Listening to High-Flying Civil Aircraft on the VHF Aero Band from the Halifax, Nova Scotia area
Bill's Radio Site
Last updated MARCH 10, 2024
This web article is intended
for use to support your listening to civil aircraft flying over the Maritimes or
landing or departing at our airports.
It is also useful in conjunction
with following aircraft on sites such as flightradar24, Planefinder and flightaware.
Author's note: Nothing said here is official. It is based entirely on observation. I have been a dedicated aviation listener for several decades.
THIS ARTICLE OVERLAPS WITH
SEVERAL OTHER OF MY AERO LISTENING ARTICLES ON MY WEBSITE (WWW.MARSCAN.COM)
AND I RECOMMEND
THAT YOU READ THEM AS WELL IF YOU FIND THE TOPIC INTERESTING.
The VHF Aero band extends from 108.0 MHz to 137.0 MHz. The bottom 10 MHz are used almost exclusively by navigation aids, and my listening therefore extends from 118.0 MHz upwards. The band is sometimes call simply "Airband" however there are other aeronautical bands (sets of frequencies) in the MF and HF parts of the spectrum. There is also a military airband ("milair") in the 225 to 400 MHz UHF range. Within the military the VHF band is sometimes referred to as "Victor" and the UHF band as "Uniform". This article refers only to the VHF airband. I am not a pilot, but have monitored the VHF airband for many years. I should say that I hardly ever just sit and listen to the exclusion of other activities. I listen in the car while commuting, but usually have the regular radio on as well. I have an airband scanner going in my den but I am usually doing something else as I listen.
It may be best to start by remarking that my listening interest will be different from yours. I think that most airband listeners like to listen in as part of visual observation of aircraft coming and going at the airport. In other words, they want to see and hear the aircraft at the same time, and generally will be sitting in their vehicle at the airport doing both. There are a few that do something similar in listening for aircraft in sight that are passing high overhead their homes. This includes those who like to listen in on American aerial refueling that commonly occurs above Nova Scotia, which occurs partially on the VHF band and partly on the military UHF band. Once you know the frequencies to program into your scanner, which can be a handheld with its attached rubber duck antenna, you will be fine, and really do not need this page.
Yes, I enjoy sitting at the airport and being able to both see and hear aircraft moving on the surface, as well as taking off and landing. I have also listened for aircraft that I can see flying high above my home, but that is not a focus of mine because I have learned that it is very rarely that they are transmitting while in my view. But let's go beyond those aspects of aero listening.
My listening tends to be a bit more abstract in nature. By that I mean that my aero listening usually does NOT involve being able to physically see the aircraft I am listening to.
At home, in my "den", I usually have my scanner turned on, listening to the VHF aero band, and sometimes other bands as well. I certainly cannot see any aircraft from there. On the other hand I have Flightradar, Flight Aware and ADBS Exchange up on the computer, and I correlate what I am hearing with what I can see on the screen. I do often listen to aircraft coming in and out of Halifax Airport, and that means I can on occasion run outside and see the aircraft I just heard. Mostly though I don't see them, and in fact I listen a lot to high-flying aircraft that are passing over the region to and from Europe.
I want to emphasize that I almost always listen on the scanner direct rather than via an internet feed. The scanner allows me to pick and choose the frequencies I want, and everythng is in real time, direct from the transmitters. It does mean however that I am restricted to listening to transmissions in range of my antenna. Once is a blue moon I do bring up an internet feed from far away when there is something special I want to hear. Internet feeds are okay, but generally they include several frequencies from a particular location, and you have no means of picking which one or ones to listen to, or to know which one you are hearing at any particular instant. Secondarily, the feeds always (or perhaps almost always) have a built-in delay of quite a few seconds. I can listen to the Yarmouth feed while I have the scanner on, and will hear on the scanner an aircraft transmit on let's say 135.2, and half a minute later hear that same transmission come over the internet feed. The only reason I listen at all to the Yarmouth feed is to get the controller's side of the conversation but it is quite strange to hear the aircraft reply to the controller before I hear the controller talk to the aircraft!!
This map will show you the area I can monitor direct from my home location. The nearly 200 nautical mile radius shown seems to be the maximum for aircraft flying at the normal 35000 to 40000 foot altitude. It is an optimistic circle, as reception drops off rapidly, and can be very low and scratchy towards the extremity of the circle. There are variations based also on the aircraft antenna and other technicalities, and I likely have some variation based on the direction from my location. I am unusual in that I have a receiving antenna intended for the VHF aero band and this is mounted on the roof. If you are using a handheld or base scanner with an attached antenna you will not get nearly as good a reception distance.
If you are listening to low flying aircraft, such as those going in and out of airports in the region, the reception distance will be much less. If an aircraft is at 5 or 6 thousand feet I will perhaps hear them out to 50 nautical miles, but that is a rough estimate.
So let's go back to high flying aircraft. They are generally flying Southwest to Northeast, or vice versa, diagonally across this map. Some are those that are originating at airports in our region and are heading west to other parts of Canada, or vice versa, and they will be flying more left-right/right-left across the map.
These high flying aircraft transmit only intermittently, and the chances of them doing so while above your home are quite low. Most commonly you will hear them checking in with the area control centre as they approach the green lines shown on the map. All of the area shown on the map (other than out to see in the New York Oceanic area) is under control of these area centres. The sequence for an aircraft coming from the US east coast is Boston Centre, then the west zone of Moncton Centre, then the East Zone, and then Gander Centre, before going out over the ocean for the crossing. This of course is the other way around for those arriving from Europe. There is a lot of variation based not only on the particular end points of the flight, but also based on wind speed and direction. Some days the West to East flights will be mostly just off the Nova Scotia coast, and other days along the spine of NS, and others more so over New Brunswick. There is far too much variation and discernable patterns to discuss meaningfully here.
You will most likely hear aircraft call the next centre as they pass over the boundary. Sometimes they receive their direction from the area they are leaving by radio. In that case you will hear them acknowledge that and say goodbye. Many times however they receive the instructions to switch via data link that you will not hear. So I might hear an aircraft check in on 132.7 as it comes out of Boston's airspace and into Moncton's, and might even just before that hear them acknowledging the directive from Boston on 134.95 or 128.05. Other than the boundary transition, you might not hear a particular aircraft at all. Sometimes they do call in along the way to ask for an altitude change, usually due to encountered turbulence, or to ask to deviate in direction, or to ask about clearances for later parts of the flight. Note that the boundaries shown are not exact, and there is a lot of variation in exactly where an aircraft will be directed to check in with the next controller, so it could be well ahead of the boundary as I have drawn them. It will not be after the boundary.
So, now for a little explanation of aero listening, referring to the map above. Aero radio is basically simplex. That means that the station communicating is on the same frequency as the station they are communicating with. Sometimes you will hear an aircraft crew speaking to another aircraft but that is relatively uncommon. Mostly they are talking to a station on the ground. What you see above are the frequencies used in my area for aircraft to talk to the area control centre responsible for the zone in which they are flying. These zones are divided into sectors that i have not shown here, and these sectors, in theory, have frequencies assigned for use within them. Commonly however the sectors are in various configurations joined together, or not, depending on traffic at the time. I have merely indicated the general area in which a frequency is used. Some of the frequencies shown are only used in heavy traffic times. So for example in the southern part of the west zone for Moncton, there are three frequencies shown, but most of the time only 135.2 is used. Over norftheast Nova Scotia and adjacent waters, in low traffic times only 125.25 is often used, then when busier, 132.75 is added, for along the spine of NS and to the north, and 125.25 offshore. In very busy times, 133.7 and/or 133.3 and/or 132.8 are added. 133.95 is only very rarely used and is intended for far offshore traffic, but experience has shown that the 125.25 generally reaches that area adequately.
Note that Moncton has further frequencies used off the map to the north into Quebec and Newfoundland and Labrador. None of these can be heard directly from my location. But I do hear them indirectly sometimes when cross-coupling (described below) is in effect.
The area control stations have locations where their personnel are sitting but they have various remote transmitter/receivers at long distances away from their home location. Moncton Centre itself is located at Riverview, New Brunswick, just across the river from Moncton itself. Boston Center is located in Nashua, New Hampshire. My map indicates how far I can hear, but that is for the aircraft that are flying at high altitudes. It certainly does not mean that I can hear the ground station that they are talking to. A ground station can only be heard for a short distance elsewhere on the ground, no matter how good your antenna. I would say that twenty miles is pretty good in that respect. So, hteer is no way I am going to be hearing that Yarmouth (xY) transmitter from my location. So I can hear aircraft when they transmit on 135.2 but I cannot hear the other side of the conversation that is being transmitted from the Yarmouth ground facility. I am very lucky to be in range of the Moncton Centre remote on `133.95, located near the Halifax Airport. That means that if an aircraft were to be talking on 133.95 with Moncton, I would hear both sides. if you live nearby to one of these remote faclities that will be the situation for you as wlll.
So, what does this mean for listening. All I can say is that if I scan all the frequencies shown above I can hear aircraft on them, if the frequency is in use at the time, and if the aircraft is more or less within that circle. I cannot hear the ground side, unless it is being transmitted on 133.95 (because I am located close to the transmitter in Halifax) and note that it is a Moncton East Zone frequency, so I am not going to be hearing the ground side of Boston Centre, the West Zone of Moncton, or any other area, at least not direct from my home. Using an internet feed does allow that, but I am talking here in this article about direct reception on the scanner.
Just a few points of interest, the Americans call their remote facilities RCAGs (Remote Communications Air/Ground Facilities) whereas in Canada they are called PALs (Peripheral Facilities). The word "center" is the US spelling and "centre" is the Canadian. In Canada they are Area Control Centres (ACC) and in the USA, Air Route Traffic Control Centers (ARTCC).
The centres operating the frequencies shown also operate other frequencies for use by lower-flying aircraft, i.e. below 29000 ft. This includes aircraft descending from higher levels and heading to airports, and vice versa, and as well aircraft that do not generally or ever fly at the higher altitudes. Air refueling takes place in the lower levels, even though the aircraft involved are perfectly capable of flying at higher altitudes and do so when not involved in AAR. For a map and list showing the low level frequencies see my article on controlled airspace and sectors. It will also show again the high level frequencies, but also including some off the area shown on this map here. Because aircraft on the low level frequencies are frequently ascending and descending significantly, the range of reception of these frequencies varies greatly, but is generally much less than the high level radius of around 200 nm shown here.
SIMULCASTING AND CROSS COUPLING IN THE AERO BAND
I have a larger article on this topic elsewhere on the site, so this will relate only to listening in on high level flights as described above.
In the simplest configuration, the ground stations of the various centres transmit and receive, each on a single frequency. For example, there is a ground station for Moncton at Sydney using 132.75 MHz. I live far away from Sydney and cannot hear the ground-based transmissions on 132.75 but I certainly can hear the aircraft that are transmitting to that station. This means I am hearing one side of the conversation only. On the other hand I do live close enough to the ground station on 133.95 located at Halifax, and if an aircraft transmits on that frequency I can hear it as well as the controller's side of the conversation. Oh and just a reminder that the Halifax transmitter is geographically located within the Moncton west zone but its 133.95 frequency is part of the east zone.
SIMULCASTING
Occasionally Moncton Centre will employ simulcasting, using all or some of its high level frequencies. When it happens it is only within the West Zone or East Zone, not the whole Moncton Centre area. In simulcasting, the Centre controller can combine several or all of the active frequencies, so that when they want to address an aircraft or reply to it, the controller does not have to select which frequency to use, they have them tied together, and pressing the transmit button will activate all the transmitters. The aircraft is only on one of the frequencies, but that one will be in the simulcast. As stated, the advantage is that controller, who is listening in simultaneously to several frequencies, does not have to select the right one when talking to the aircraft. The possible downside to this arrangement is that the crew on the aircraft will hear a lot of transmissions from the controller that are not even for their sector.
Keep in mind that I am close enough only to the Halifax transmitter using 133.95 MHz. In simulcasting I can hear the words that are being transmitted on the ground stations in Sydney and the Magdalen Islands and as well other stations off the top of the map above, because they are also being transmitted over the Halifax transmitter. If I keep the scanner on scan, I will hear the controller on 133.95 and the aircraft as well on 133.95 if that is the one they are using, but also aircraft in my range (within the circle on the map) as they transmit on 125.25, 132.75, etc.
CROSS-COUPLING
Cross-coupling is utilized more commonly than simulcasting in the Moncton region, at least according to my observations. Cross-cgcoupling is a step beyond simulcasting. In this configuration what is received on any ground station is retransmitted on all the others that have been selected. Just as with simulcasting, the controller can select which statons to join together.
So let's say it is not really busy, and one controller is working the whole east zone for Moncton Centre. You can see the southern part of the zone on the map above, but keep in mind it also extends off the top of the map northwards to just south of Goose Bay in Labrador. Whatever is being transmitted from aircraft on any of the zone's frequencies will be retransmitted on all the ground stations. As I stated earlier, I am in range of the East Zone transmitter at Halifax, on 133.95. If there is a full zone cross-coupling. I can listen on 133.95 and hear what is being received and sent through all the other ground stations that are in the zone, including those shown at Sydney (4 transmitters) and the Magdalen Islands, as well as the ones in Stephenville, NL and Natashquan, Quebec, that are not shown. All will be coming through the 133.95 transmitter at Halifax, and I mean both sides of the conversation, loud and clear. Cross-coupling is wonderful but keep in mind it is not always in effect. In very busy times there will be several controllers working the Moncton East area, and while there might be smaller groups of cross-coupled transmitters, you won't hear the whole zone. This also happens in the west zone, but as I am not in range of a west zone ground transmitter it is irrelevent to me, unless I am using an internet feed. in that case if I bring up a feed from Yarmouth or Moncton I should be able to hear the West Zone in the same way I hear the East.
I myself have a fascination for radio itself and like to hear the aircraft direct to my antenna and radio, but on the other hand it is great to be able to just sit on 133.95 and get the whole east zone, as frequently happens.
I am not sure if cross coupling, or simulcasting for that matter, are used by Boston Center or indeed any other centres.
JUST A WORD ABOUT IDENTIFYING AIRCRAFT
I do recommend highly that if listening in to the high level frequencies that you also have FlightRadar24 or another tracking app up on your laptop or phone. You can pick up the aircraft you are seeing and follow their progress. Aircraft are identified on air and on the map by flight numbers. What you hear should correlate with what you see. That is the numerical part. There is also a callsign part of the identification. On the map you will see for example AAL in front of an American Airlines flight number, but on the radio the spoken callsign is "American" followed by that number, and hardly ever will you hear the AAL spoken. But you also must realize that many airlines and business aircraft operators use spoken callsigns that differ from the company name. For example British Airways uses "Speedbird" and Porter Airlines Dash 8 aircraft use "Dashport". For a guide to airline codes and spoken callsigns see my special page. Note that some corporate aircraft do not use "code and number" identifiers but instead use the aircraft's registration marks, e.g. C-GRSY or N458AP or similar, also explained on that page.